Fire behavior of steel and partially encased composite columns embedded on walls

Abstract

This paper presents the results of an experimental research on steel and composite partially encased steel columns embedded on brick walls and subjected to fire. The specimens were made of HEA 100 and HEA 220 steel profiles, with the web parallel and orthogonal to the wall's surface. The thickness of the tested walls was 7, 11, and 15 cm depending on the steel profile used in the column. Due to the generated thermal gradient, this type of columns experienced thermal bowing, bending first towards the exposed side and then to the opposite side of the fire. When the column's web is parallel to the wall's surface, a less pronounced thermal gradient is developed, and the column behaves more like to a uniform heated one. The axial restraining forces increasing and after reaching the peak value decreasing quite suddenly. When the column's web is orthogonal to the wall's surface, the steel flange is directly exposed to fire, resulting on its rapid thermal elongation accompanied by a rapid degradation of the mechanical properties of the materials, while the remaining cross-section heats slower. The restraining forces after reaching a peak value descended a little bit and then increasing again up to second peak value, thus part of the cross-section is slowly heating and elongating. The thickness of the brick wall influenced the stiffness of the tested columns, affecting the development of the restraining forces and displacements.